Various apparatus have been developed to provide a speed reduction for an engine. An assembly of gear trains, which may incorporate clutches to engage differing gear ratios, is one of the most common; however, such an assembly suffers from a drawback of providing only a finite number of reduction ratios. A planetary gear system suffers from the same drawback. Both such gear systems are hampered by the possibility of premature failure of one of the gear members. An assembly of pulleys and belts may also be used for varying the torque output produced by an input shaft; however, breakage of a belt, which also results in failure of the system, motivates against the use of a pure belt and pulley arrangement. Belts and pulleys, however, allow for a certain amount of slippage in an overload condition. Accordingly, an apparatus comprised of a gear arrangement and a pulley-belt arrangement provides a speed reducing capability in the transmission of torque incorporating the desirable features of the straight gear arrangement and the straight pulley-belt arrangement. A redundant pulley-belt arrangement so that failure of one belt does not result in failure of the system provides an even more reliable and longer lived system.